Tampon applicators which include a pair of telescoping cylinders are well known in the art. For example, Berger, U.S. Pat. No. 3,895,634, assigned to the assignee of the subject application, and Voss U.S. Pat. No. 3,433,225 typically show such applicators in which the pledget is initially stored in the forward end of a cylindrical barrel. A lesser diameter plunger is telescopingly contained within the rear end of the barrel, such that the forward end of the plunger abuts the rear end of the pledget. Advantageously, the forward end of the barrel, which is inserted in the vagina prior to tampon injection, includes a smooth, dome-shaped end for the user comfort. When the user then urges the plunger against the rear end of the pledget, the pledget is moved forwardly in the barrel, opening up the petals which form the dome-shape forward end of the barrel, as the pledget is ejected from the barrel. Following the full ejection of the tampon pledget, the petals then return towards their original closed position so as to comfortably remove the applicator from the body orifice. Such tampon applicators are conventionally manufactured either of a suitable plastic composition, which is typically injection molded, or from cardboard. In view of environmental concerns, cardboard applicators, which are water degradable or water dispensable, are increasingly desirable. The force necessary to eject the tampon from a plastic applicator can be controlled by the composition and thickness of the plastic material, while maintaining the necessary structural integrity for the barrel. For example, in the aforementioned Berger U.S. Pat. No. 3,895,634 the cross-sectional wall thickness of the tubular portion of the barrel member and petals forming the dome-shaped insertion tip are different, to provide a relatively high strength side wall for the main body portion of the barrel and a relatively flexible and supple insertion tip. This provides the requisite stability for the barrel proper and an acceptable tampon ejection force. Achieving these desirable characteristics in a cardboard applicator is somewhat more difficult due to the limited degree to which the characteristics of the cardboard may be varied, as opposed to modifying the composition of the plastic, and the relative stiffness of cardboard layers which are of sufficient thickness to provide the requisite structural integrity for the barrel.
Various techniques have previously been proposed for modifying the forward end of such dome-shaped cardboard applicators which have petal defining slits to appropriately adjust the pledget ejection force. For example Wiegner, et al. U.S. Pat. No. 4,412,833 and Beastall et al. U.S. Pat. No. 4,087,239 provide an indented circumferential groove (which can take the form of slots or perforations in Beastall) at the end of the slits located at the base of the dome-shaped tip to provide a hinge region for the bending of the petals. Such a hinge had also been disclosed in aforementioned Voss et al. U.S. Pat. No. 3,433,225. Whitehead U.S. Pat. No. 4,508,531 and Decker U.S. Pat. No. 4,453,925 show a series of transverse score or relief lines along the length of the cardboard petals in a tampon applicator to facilitate their bending into a round tip.
While such prior techniques have been found to aid in the formation of the dome tip and lower or otherwise control the ejection force of the tampon pledget, they are less than fully satisfactory in appropriately optimizing the ejection force, while maintaining all the other desirable tampon applicator characteristics. Further, recognizing that some variations are to be expected in the mass production of tampon applicators it is desirable to provide for anticipated manufacturing tolerances to assure that appropriate ejection forces will still be maintained within the anticipated range of product variations.